Extraction of polysaccharides from quinoa (Chenopodium quinoa Willd) bran using deep eutectic solvent: Isolation, structural characterization, and hypoglycemic activity

Quinoa ( Chenopodium quinoa Willd) contains various bioactive compounds, such as polysaccharides, polyphenols, and flavonoids. However, studies on the efficient extraction of polysaccharides from quinoa bran are lacking. In this study, the process of extracting polysaccharides from quinoa bran (QBP) using ultrasound-assisted deep eutectic solvents (DESs) was optimized, and the yield was 14.13 ± 0.53 % under optimal conditions. The polysaccharide was purified to obtain the polysaccharide fraction UDES-G-QBP2 with a molecular weight of 1.75 × 10 4 Da, consisting of galactose (3.79 %) and glucose (96.21 %). Methylation and nuclear magnetic resonance analyses revealed that UDES-G-QBP2 was mainly composed of →4)-α-D-Glcp-(1→ and →4,6)-α-D-Glcp-(1→ connected to each other to form the main chain, and the branched chain was mainly composed of α-D-Glcp-(1→ connected to the O-6 position of →4,6)-α-D-Glcp-(1→. UDES-G-QBP2 presents triple-helix conformations. The activities of α-amylase and α-glucosidase were inhibited by UDES-G-QBP2 in a dose-dependent manner. Furthermore, UDES-G-QBP2 promoted glucose consumption and glycogen synthesis in insulin resistant (IR) HepG2 cells. UDES-G-QBP2 also protected HepG2 cells from IR co-induced with high-glucose and insulin by activating the PI3K/AKT/GSK-3β signaling pathway. The results reveal that UDES-G-QBP2 could serve as a potential anti-diabetic dietary supplement. • Optimized polysaccharide extraction from quinoa bran using ultrasound-assisted DESs. • Yielded UDES-G-QBP2’s proposed structure with a Mw of 17.5 kDa, comprising 96.21 % glucose and 3.79 % galactose. • Featured a triple-helix structure and inhibited α-amylase and α-glucosidase dose-dependently. • Protected HepG2 cells from insulin resistance via the PI3K/AKT/GSK-3β pathway.